Hi @Salman,
I recommend watching Winston’s MaterialMonday videos:
The first two cover cutting aluminium, with recommended feeds and speeds.
I highly recommend getting single-flute ZrN coated cutters (for example #278Z on the C3D store), they are much more forgiving than three-flute in aluminium, especially if you are going to do contour (slotting) cuts.
The diameter of the cutter to be used will of course depend on the size of the text you want to cut, so you may need to go smaller than 1/4".
Note sure what you mean by “26” aluminium though ? The aluminium grades are usually referred by a four number code e.g. 6061